• International Journal of Naval Architecture and Ocean Engineering
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• 제6권2호
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• pp.206-218
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• 2014

The wave attenuation by floating breakwaters in high amplitude waves, which can lead to wave overtopping and breaking, is examined by numerical simulations. The governing equations, the Navier-Stokes equations and the continuity equation, are calculated in a fixed Cartesian grid system. The body boundaries are defined by the line segment connecting the points where the grid line and body surface meet. No-slip and divergence free conditions are satisfied at the body boundary cell. The nonlinear waves near the moving body is defined using the modified marker-density method. To verify the present numerical method, vortex induced vibration on an elastically mounted cylinder and free roll decay are numerically simulated and the results are compared with those reported in the literature. Using the present numerical method, the wave attenuations by three kinds of floating breakwaters are simulated numerically in a regular wave to compare the performance.

• 대한공간정보학회지
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• 제8권2호
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• pp.101-108
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• 2000

단시간으로 많은 3차원 지형정보를 획득할 수 있는 GPS 이동측량은 수 km 이하의 단기선에서 주로 활용되고 있으며, 장기선에 대한 위치결정은 비교적 오랜 시간이 요구되는 정지 측량에 의존하고 있어 단시간으로 장기선 위치결정을 할 수 있는 방법이 요구되고 있다. 본 연구는 GPS에 의한 장기선 이동측량의 효율적 이용 가능성을 검토하기 위하여 수 십 km 이상의 기선에 대한 기선 거리별, 궤도력별 그리고 관측시간대별로 기선해석 정확도를 정지측량 결과와 비교 분석하고자 한다. 연구결과, cycle slip이 발생한 경우 기선해석 정확도가 크게 저하됨을 알 수 있었다 정밀궤도력을 이용한 경우 70km 이내에서 수 분의 이동측량으로 1ppm 이하의 정확도를 얻을 수 있었다. 앞으로 좀더 심도 있는 연구가 수행된다면, 수 십 km 이내에서 GPS 이동측량을 이용하여 국토개발을 비롯한 각종 건설분야에 필요한 지형정보를 보다 효율적으로 획득할 수 있을 것으로 기대된다.

• 한국소음진동공학회논문집
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• 제16권11호
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• pp.1172-1178
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• 2006

Measurement of blade strain with sensors directly installed on the blade has one critical issue, how to send the sensor signal to the ground. Strain-gauges have been dominantly used to directly measure stress of a blade and either a slip ring or a telemetry system has to be used to send measured signal to the ground. However, both systems have many inherent problems and sometimes very severe limitations to be practically used. In this paper, new on-line strain monitoring method using. FBG(Fiber Bragg Grating) sensors and a beam coupler is introduced. Measurement of rotor stress using FBG sensors is nothing new, but unlike other system which installs all necessary instruments on the rotor and use telemetry system to send data to the ground, this system makes use of light's unique characteristic - light travels through space. In this new approach, single optical fiber with many FBG sensors is installed on the blade and all other necessary instruments can be installed at ground thereby giving tremendous advantages over slip ring or telemetry system. A reference sensor is also introduced to compensate the beam coupler's transmission loss change due to rotation. The suggested system's good performance is demonstrated with experiments.

• 한국자동차공학회논문집
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• 제2권1호
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• pp.84-95
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• 1994

The effects of punch and blank shapes in the rectangular cup drawing process are examined experimentally to improve the formabilities. For this purpose, three blank shapes which are h-bl., G-bl., and T-bl., and five punch shape factors which are the ratios of two adjacent side lengths in rectangular cross section are adopted. The constructing methods of the three blank shapes are as follows. The h-bl. is designed by slip-line theory, and the G-bl. is selected for the similar shape to the punch. The T-bl. is obtained by the drawing method which is introduced in the technical references. The five punch shape factors are selected for length/width=1, 1.25, 1.5, 1.75 and 2. The experimental procedures are performed for all the above forming conditions to investigate and compare the formabilities. As a result, it is verified experimentally that the rectangular cups drawn by the h-bl. are more ideal than those drawn by G-bl. and T-bl.. They have not only higher limiting drawing ratio, more uniformity in drawn cup heights and more ideal thickness distributions, but also need relatively less maximum drawing forces.

• Applied Microscopy
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• 제35권4호
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• pp.64-73
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• 2005

이 논문에서 한 결정체의 전위 결함에 형태를 결정짓는 인자들 (Burgers-벡터, Slip plane, 전위선 벡터)을, LACBED 방법과 전통적인 회절 빔 상 관찰에 의해, 어떻게 얻을 수 있는가에 대해 세세히 논의하였다. 이 방법은 기본적으로 Cherns과 Prestons의 규칙과 동역학적 회절이론에 입각한 공식에 의거한 LACBED 패턴 시뮬레이션이 따른다. 이 시뮬레이션 계산에서 필요에 따라 설정된 여러 근사들에 관해서도 역시 세세히 논의 하였다. 본 실험에 사용된 시료는 적적한 밀도로 분포된 전위 결함들을 많이 갖고 있는 순순 알루미늄이며, LACBED 실험에 적합한 것이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.711-713
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• 2003

This paper deals with the improvement of starting characteristic of line-start synchronous relucatance motor(SynRM). To decide the number of conductor bars, the locking torque, when slip is 1, is computed by finite element method(FEM). And then, the magnetic circuit is designed to improve the starting torque according to the rotor position from the shape design of the conductor bars of the rotor with the flux barriers.

• 한국정밀공학회지
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• 제21권12호
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• pp.92-99
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• 2004

The formation degree of sustain (ITO pattern) decides quality of PDP (Plasma Display Panel). For this reason, it makes efforts in searching defects more than 30 un as 100%. Now, the existing inspection is dependent upon naked eye or microscope in off-line PDP manufacturing process. In this study developed prototype inspection system of PDP 170 glass is based on line-scan mechanism. Developed system creates information that detects and sorts kinds of defect automatically. Designed inspection technology adopts multi-vision method by slip-beam formation for the minimum of inspection time and detection algorithm is embodied in detection ability of developed system. Designed algorithm had to make good use of kernel matrix that draws up an approach to geometry. A characteristic of defects, as pin hole, substance, protrusion, are extracted from blob analysis method. Defects, as open, short, spots and et al, are distinguished by line type inspection algorithm. In experiment, we could have ensured ability of inspection that can be detected with reliability of up to 95% in about 60 seconds.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.191-195
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• 2003

The formation degree of sustain (ITO pattern) decides quality of PDP (plasma display panel). For this reason. it makes efforts in search defects more than 30 ${\mu}{\textrm}{m}$. Now, the existing inspection process is dependent upon naked eye or SEM equipment in off-line PDP manufacturing process. In this study developed prototype inspection system of PDP ITO glass. This system creates information that detects and sorts kind of defect automatically. Design ed inspection technology adopts line-scan method by slip-beam formation for the minimum of inspection time and image processing algorithm is embodied in detection ability of developed system. Designed algorithm had to make good use of kernel matrix which draws up an approach to geometry. A characteristic of area-shaped defects, as pin hole, substance, protrusion et al, are extracted from blob analysis method. Defects, as open, short, spots, et al, are distinguished by line type inspection algorithm. In experiment results, we could have ensured ability of inspection that can be detected with reliability of up to 95% in about 60 seconds

• 대한기계학회논문집
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• 제1권3호
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• pp.164-170
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• 1977

Johnson 의 직교이방성재료압출시의 slip line 해를 모아레법으로 검토하였다. 모아레식편상에 slipline 장과 유사한 모아레무늬를 얻어 이론해와 비교하였으며, 모아레무늬 해석법으로 변형후의 상당스트레인 속도분포를 구하였다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제34회 추계학술대회 개최
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• pp.364-373
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• 2001

This paper describes the variation of lubricant's temperature effects on elastohydrodynamic lubrication. The Newton-Raphson technique was used to solve the simultaneous system of Reynolds and elasticity equations. To show effects of lubricant's temperature, average temperature across the oil film was calculated using the energy equation. Pressure distribution, film shape, and temperature distribution were obtained for fully flooded conjunctions, and various dimensionless speed parameters while load and material parameters were held constant. Minimum film thickness were obtained for various material properties while load and velocity were held constant. It is drawn that the thermal effects have a strong influence on a minimum film thickness under high rolling velocity and slip ratio.